Haiyan, which is known locally as Yolanda and carried winds of 195mph, killed more than 6,000 people and left 4 million displaced, are likely to be increasingly common in the era of climate change, they say, making the situation for those in temporary accommodation all the more perilous.

“This is a reality for the world, and it’s certainly a reality for the Philippines,” said Jennifer MacCann, operation director in the country for the charity World Vision. “There will be bigger storms, they will have much more of an impact, and we should expect them.”

Despite intensive relief efforts by the Philippines government and international agencies, including £95m raised from the British public by a Disasters Emergency Committee appeal, aid teams say more than 2.5 million people in the region hit by typhoon Haiyan remain without proper homes. At least 100,000 are living in coastal areas officially declared unsafe, many in temporary shelters made from tarpaulins or plastic sheeting.

Mentally ill people found chained by families and left to die after typhoon Haiyan

Adding to the safety worries is the fact that many of the communal typhoon shelters which saved thousands of people from Haiyan, often schools, churches and community centres, remain damaged or destroyed.

A study by the International Migration Organisation (IOM) in April found that in Samar province, one of the areas worst hit, of 634 official evacuation shelters only 8% remained intact, with a quarter completely destroyed and 400 more needing major work. Subsequent storms have seen more demand for the remaining communal centres as many homes remain unsafe, said the IOM, describing the Philippines as “on the front line of climate change”. According to MacCann, it could take five years to get people into safe homes.

In July, the country was battered by another major storm. Typhoon Glenda killed more than 100 people.

If a major typhoon was to strike the areas devastated by Haiyan again in the near future, there is the potential for catastrophe, said Alison Kent, Oxfam’s humanitarian policy advisor in the Philippines. “That’s the key thing with evacuation centres, they’re such a critical way to minimise loss of life. With such a big storm as Haiyan to have an estimated 6,000 fatalities, given the extent of the damage, the loss of life could have been much greater. But now, in the absence of some of those evacuation facilities, it’s a big concern.”

Another big storm would also wreck efforts to resuscitate the region’s economy, after Haiyan devastated farmland, coconut plantations and fishing fleets.

This was a particular problem away from the region’s main city, Tacloban, said Laura Gilmour of Care International: “It’s people in these remote areas [who] are more vulnerable anyway, because they don’t have the land, or they’re completely dependent on something like coconut farming, which has been completely wiped out. They are now in huge debt, still having to pay landowners even if they have no crops.”

Several charities report significant numbers of people leaving Haiyan-hit areas for Manila or other cities, including women who have entered the sex industry to support their families.

Saño is currently halfway through a 620-mile (1,000km) walk from Manila to Tacloban to raise awareness of the effect of climate change on a country with more than 20,000 miles of coastline. He aims to arrive on the anniversary of the day Haiyan made landfall, 8 November.

“It’s three years in a row that we’ve been hit by super-storms, and we had another strong one last July,” he told the Guardian. “We are barely scratching the surface when we talk about addressing the root causes of all this. It’s all connected to these causes – poverty, environmental degradation, governance. All of these things combined could lead to disastrous consequences.”

During the walk, Saño said, he was collecting people’s experiences of how climate change affected them. The cumulative impact was overwhelming, he said. “They’re telling us about how things have changed for the worst compared to several years ago, with storms, punishing droughts, and erratic rainfall patterns. One of the things we’re doing on this walk is documenting these stories from ordinary Filipinos so we can tell the whole world about them.”